1. Field of the Invention
The present invention relates to a fuel control system for a carburetor, used in combination with an internal combustion engine particularly adapted accurately to meter the fuel requirements for small, four-cylinder engines having displacements of 100 to 150 cubic inches.
2. Description of the Prior Art
Carburetors having variable venturi plates utilized to meter fuel for all operational modes of an internal combustion engine are well known. A carburetor of this type is disclosed in U.S. Pat. No. 4,283,355 to Pollution Controls Industries, Inc. of Tulare, Calif., issued on Aug. 11, 1981.
The carburetor disclosed in the aforementioned patent is characterized by pivotally positionable venturi plates whose movement is precisely coordinated with that of a fuel metering element adapted to provide a desired air-fuel mixture ratio at all positions of the plate, and particularly at positions of the plates corresponding to relatively low flow of air through the carburetor, as during idling and other low-speed operations. While the carburetor disclosed in this U.S. Pat. No. 4,283,355, functions quite well for metering large amounts of fuel for engines of displacement of 300 cubic inches or more, it does not function as well for engines of 100 through 150 cubic inches, which consume proportionately smaller amounts of fuel.
Research conducted on the problems associated with metering these small amounts of fuel has shown that the mechanical system disclosed in the aforementioned patent does not work as well in the smaller engines because the precision required to produce the elements that comprise the invention cannot be achieved in a cost-effective manner. The present invention overcomes these problems of the prior art by providing a fuel control system that has a primary and secondary system. The primary system, herein disclosed, provides fuel to the carburetor for idling and part throttle operation, and the secondary system meters fuel for wide-open throttle operation only.
According to the present teaching, a fuel control system for a carburetor is provided having a primary restrictor and a primary adjustable jet which provide fuel to a nozzle bar that is located in the throat of the carburetor equipped with symmetrically disposed, pivotally positionable venturi plates. The fuel supplied by the primary restrictor and the primary adjustable jet constitute the primary fuel supply system for idling and partthrottle operation of the engine. A secondary restrictor is provided which has a mechanical metering system adapted to control the fuel provided from the secondary restrictor to the fuel being provided from the primary adjustable jet and the primary restrictor. The metering system that controls the fuel moving from the secondary restrictor is connected to, and its movement corresponds with, the movement of the symmetrically disposed venturi plates which are pivotally positioned in the throat of the carburetor. The movement of the pivotally positionable venturi plates is largely a function of the mass of air flow moving through the throat of the carburetor.
This approach allows for the effective metering of the small amounts of fuel required by engines of small displacement. This approach furthermore overcomes the problems of the prior art in that the precision required to produce the elements of the prior art patent is not required of a carburetor of this particular design.